There will be a SNES app and an N64 app next year, I think.
But I also think they will each be treated as an add-on subscription to Nintendo Online Services, maybe like $10-20 more a year per system.
NES games, and by extension SNES games etc, aren't just a bonus feature of Nintendo Online Services. They're
exclusive to NOS. There's no more ala carte, you can't just get the games you want. You either sub to NOS or you don't get VC. And regardless, you can never
own VC titles on Switch.
My conviction that this is the plan is only strengthened by the fact that the NES replica controllers for Switch that they are selling for $60/pair only work with the NES app and nothing else. Or to put it another way, the controllers are completely useless if you aren't subscribed to Nintendo Online Services.
The box even has prominent "ONLINE" branding.